Add spring-boot-microservices-project: config server, Eureka, gateway and three services on Boot 4.1.1 + Spring Cloud 2025.1.3

Product, order and inventory services behind Spring Cloud Gateway (WebMVC), configuration from a Config Server,
discovery with Eureka, a Resilience4j circuit breaker on order -> inventory and Brave tracing. Run as six plain jars;
output/ holds real transcripts (config, registry, requests, trace propagation, circuit breaker, startup race and the
load-balanced RestClient.Builder trap). Dockerfile and docker-compose.yml are included but were not run.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01HhW8LD8r3EigoBaCGrQZx5

gateway/src/main/java/com/ankurm/shop/gateway/GatewayApplication.java

@@ -0,0 +1,12 @@
+package com.ankurm.shop.gateway;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/** The single public entry point. The routes are in config-server/src/main/resources/config/gateway.yml. */
+@SpringBootApplication
+public class GatewayApplication {
+    public static void main(String[] args) {
+        SpringApplication.run(GatewayApplication.class, args);
+    }
+}

gateway/src/main/java/com/ankurm/shop/gateway/RequestLogFilter.java

@@ -0,0 +1,32 @@
+package com.ankurm.shop.gateway;
+
+import jakarta.servlet.FilterChain;
+import jakarta.servlet.ServletException;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Component;
+import org.springframework.web.filter.OncePerRequestFilter;
+
+/**
+ * Logs one line per request. It runs inside the tracing filter, so the line carries the trace id the gateway
+ * created (or accepted from the caller) and passes on to every service behind it.
+ */
+@Component
+class RequestLogFilter extends OncePerRequestFilter {
+    private static final Logger log = LoggerFactory.getLogger(RequestLogFilter.class);
+
+    @Override
+    protected boolean shouldNotFilter(HttpServletRequest request) {
+        return !request.getRequestURI().startsWith("/api/");
+    }
+
+    @Override
+    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain chain)
+            throws ServletException, IOException {
+        log.info("gateway received {} {}", request.getMethod(), request.getRequestURI());
+        chain.doFilter(request, response);
+    }
+}

gateway/src/main/resources/application.yml

@@ -0,0 +1,16 @@
+spring:
+  application:
+    name: gateway
+  config:
+    # Fail fast if the config server is not up: a service with the wrong config is worse than no service.
+    import: "configserver:${CONFIG_URL:http://localhost:8888}"
+server:
+  port: 8080
+eureka:
+  client:
+    service-url:
+      defaultZone: ${EUREKA_URL:http://localhost:8761/eureka}
+  instance:
+    hostname: ${EUREKA_HOSTNAME:localhost}
+    # Register the service name + port as the instance id so two copies of one service do not collide.
+    instance-id: ${spring.application.name}:${server.port}